1. Field
The presently disclosed subject matter relates to illumination apparatuses having scanning laser source and vehicle headlights including the illumination apparatus, and more particularly to rotary mirror optical deflector apparatuses having scanning laser source, a high reliability and a long life, which can be easily manufactured with a high accuracy by using Micro-Electro-Mechanical System (MEMS) technology, and a vehicle headlight including the optical deflector apparatus having a high visibility without a flicker of light, even when the optical deflector apparatus is driven by a comparative low frequency to maintain the high reliability and the long life.
2. Description of the Related Art
An optical deflector apparatus, which incorporates a light source such as a laser diode and the like, has been used as a light-emitting scanner for a projector, a bar-code reader, a laser printer, a head-up display, etc. A vehicle headlight, which uses the optical deflector apparatus including a rotary mirror optical deflector that is made by using Micro-Electro-Mechanical System (MEMS) technology, is disclosed in Patent Document No. 1 (US Patent Publication No. 2011-0249460-A1). FIG. 24 is a schematic cross-sectional view depicting a conventional headlight including the optical deflector apparatus, which is disclosed in Patent Document No. 1.
The conventional headlight 300 includes: a common projector lighting 350 projecting a common light distribution pattern; a pair of laser devices 310 each having an optical axis emitting laser beams along each of the optical axes; a pair of optical deflectors 330 each having a rotatable mirror 330M in two dimensional directions, which intersect with respect to each other at a substantially right angle, each of the rotatable mirrors 330M intersecting with a respective one of the optical axes of the laser devices 310, and each of the pair of optical deflectors 330 facing with respect to each other; a phosphor panel 320 including at least one wavelength converting material, being located opposite the pair of laser devices 310 with reference to the pair of optical deflectors 330; a projector lens 340; and wherein each of the pair of optical deflectors 330 scans the laser beam emitted from a respective one of the pair of laser devices 310 in the two dimensional directions toward the phosphor panel 320, the phosphor panel 320 wavelength-convert said scanned laser beam into light having a substantially white color tone and the light having the substantially white color tone is projected in a light-emitting direction of the headlight 300 via the projector lens 340.
FIG. 25 is a front view showing an exemplary light distribution pattern on an imaginary screen, which is projected by the conventional headlight 300. The conventional headlight 300 may provide the common light distribution pattern CLDP by turning on the common projector lighting 350, and also may provide various light distribution patterns by scanning the laser light emitted from the respective one of the pair of laser devices 310 in the two dimensional directions toward the phosphor panel 320 with each of the rotatable mirrors 330M in accordance with traffic conditions.
For example, when vehicles do not exist in a forward direction of a subject vehicle incorporating the headlight 300, the headlight 300 may provide an elbow light distribution pattern ELDP in addition to the common light distribution pattern CLDP to improve a view in the forward direction of the subject vehicle, while preventing an emission of a glare type light toward oncoming vehicles. When the vehicles do not also exist on an oncoming lane as well as a driving lane in the forward direction of the subject vehicle, the headlight 300 may provide a high beam distribution pattern HBDP to further improve the view in the forward direction of the subject vehicle.
In addition, when the subject vehicle turns right or left, the headlight 300 may provide a right side distribution pattern RSDP or a left side distribution pattern LSDP to improve a view of corner in a rightward or leftward direction of the subject vehicle, respectively. When a driver of the subject vehicle drives under a rainy weather, the headlight 300 may emit an under light distribution pattern ULDP for the driver to improve a view of near portion in the forward direction of the subject vehicle so as to be able to prevent repelling water toward pedestrians.
As a conventional optical deflector made by using the MEMS technology, the rotary optical deflectors are disclosed in Patent Document No. 2 (Japanese Patent Application Laid Open JP2005-128,147), Patent Document No. 3 (Japanese Patent No. 4,092,283), Patent Document No. 4 (Japanese Patent No. 4,926,596), etc. FIGS. 26a and 26b are a schematic enlarged top view and a schematic enlarged cross-sectional view for explaining a fundamental principle of the conventional rotary optical deflectors, which are disclosed in Patent Documents No. 2 to No. 4, respectively.
The conventional optical deflector 200 includes: a mirror 231 configured to reflect a laser beam; an inner frame 223 formed in a shape of picture frame, and supporting the mirror 231 via a first pair of torsion bars 240A and 240B, each of the first torsion bars 240A and 240B located between the inner frame 223 and the mirror 231 and being located opposite to one another so as to rotate the mirror 231 in a turning direction of the first torsions bards 240A and 240B with a first actuator; an outer frame 221 also formed in a substantially shape of picture frame, and supporting the inner frame 223 along with the mirror 231 via a second pair of torsion bars 250A and 250B, each of the second torsion bars 250A and 250B located between the inner frame 223 and the outer frame 221 and located opposite to one another so as to rotate the mirror 231 in a direction perpendicular to the turning direction of the first torsions bards 240A and 240B with a second actuator; and therefore a first space 222 A included between the mirror 231 and the inner frame 223, and also a second space 222B included between the inner frame 223 and the outer frame 221.
The conventional optical deflector 200 can rotate the mirror 231 in two dimensional directions, which are perpendicular to each other. By combining the mirror 231, which may rotate in the two dimensional directions, with a light source such as a laser diode and the like, an optical deflector apparatus may be used as a light-emitting scanner for a projector, a bar-code reader, a laser printer, a head-up display, etc. The optical deflector apparatus including the light source may also be used as a light source for vehicle headlights, which can provide drivers with favorable light distribution patters in accordance with various road conditions, as described above with reference to Patent Document No. 1.
When the optical deflector is used as the light-emitting scanner for vehicle lamps, which may prevent a flicker of light emitted from the vehicle lamps, for example, Non-Patent document No. 1 (ISAL 2013 Page 340 to 347 [Glare-free High Beam with Beam-scanning]) discloses that the optical deflector should be driven by a power supply having a frequency of 220 Hz or more (or frame rate of 220 frame per second). However, the optical deflector is required to be driven by a lower frequency (e.g., less than 100 Hz) in view of reliability, a life, durability and the like of the vehicle lamps.
The above-referenced Patent Documents, additional Patent Documents and Non-Patent Document are listed below, and Japanese Patent Documents therein are hereby incorporated with their English abstracts in their entireties.    1. Patent Document No. 1: U.S. Patent Publication No. 2011-0249460-A1    2. Patent Document No. 2: Japanese Patent Application Laid Open JP2005-128,147    3. Patent Document No. 3: Japanese Patent No. 4,092,283    4. Patent Document No. 4: Japanese Patent No. 4,926,596    5. Non-Patent Document No. 1: ISAL 2013 Page 340 to 347 [Glare-free High Beam with Beam-scanning]    6. Patent Document No. 5: Japanese Patent No. 4,138,196    7. Patent Document No. 6: Japanese Patent No. 4,807,901    8. Patent Document No. 7: Japanese Patent No. 4,662,112    9. Non-Patent Document No. 2: ISAL 2013 Page 262 to 266 [Flickering effects of vehicle exterior light systems and consequences]    10. Patent Document No. 8: U.S. Pat. No. 8,345,096    11. Patent Document No. 9: U.S. Patent Publication No. 2013-0,242,100-A1
The disclosed subject matter has been devised to consider the above and other problems, features, and characteristics. Thus, embodiments of the disclosed subject matter can include illumination apparatuses having a high reliability and a long life, which can be used as a lighting unit for vehicle lamps such as a headlight. The disclosed subject matter can also include illumination apparatuses having a high reliability, which can emit scanned beams having various color tones including a while color tone by associating a wavelength converting member including a wavelength converting material with a light source such as a laser diode, a light-emitting diode and the like so as to be able to be used for a stage lighting, a room lighting for warming up events and the like in addition to the vehicle lamps.